This competing renewal application is focused on the role of loss of imprinting of the insulin-like growth factor II gene (LOI of IGF2) in cancer predisposition, particularly colorectal cancer (CRC). It follows directly from several major discoveries in the current grant period, including among other work: that LQI of lGF2 is associated with a positive family history of CRC and a positive personal history of colorectal neoplasia;discovery of altered epithelial progenitor cells in the normal mucosa of patients with LOI;development of an animal model demonstrating a progenitor cell defect caused by LOI, that cooperates with genetic mutations to cause tumors;and development of an independent chemical carcinogenesis model showing that LOI increases tumor predisposition, specifically mediated through IGF2 signaling and abrogated by signaling receptor blockade. In the renewal period we plan three highly related and well integrated aims. In Aim i, we will determine the mechanisms by which LOI leads to dynamic changes in IGF2 signaling, and how this may affect cellular proliferation, apoptosis, and differentiation. We will use a novel microfluidics chip and an integrated systems biology approach to model IGF2 signaling, of both canonical and noncanonical pathways discovered through the other aims of the grant. We will exploit our ability to develop both stem cell (ES) and differentiated (MEF) lines from LOI, wild type, and IGF2 knockout mice. In Aim 2, we will determine the effect of LOI on tumorigenesis in mice with a mutation in the Ape gatekeeper gene for intestinal neoplasia, and in a mouse carcinogen model, and by comparing cancers and normal tissues of patients with and without LOI. In Aim 3, we will collaborate with the NCI's Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial. We will determine the stability of LOI of IGF2 over several years, perform a nested case- control study to determine whether LOI of IGF2 in blood is predictive of colorectal adenomas and cancers, and identify genetic determinants of LOI and its consequences. These three aims, representing a novel and powerful in vitro approach to IGF2 signaling, two complementary in vivo models of LOI-mediated tumorigenesis, and a genetic epidemiology approach to LOI- mediated cancer risk that takes advantage of an extraordinary national resource, are highly integrated and reinforcing, in that they each generate data and ideas of immediate use to the other aims. Given that LOI of IGF2 may represent the first common genetic or epigenetic cancer risk marker, and the strong evidence from the current grant period supporting its role in tumorigenesis, these studies offer a substantial potential impact on cancer surveillance and prevention.